Form of government, political form, regime of government, political regime, system of government, political system, system of government, model of government or political model are some of the diverse ways of naming an essential concept of political science and the theory of State or constitutional right. It refers to the model of organization of constitutional power adopted by a State in terms of the relationship between the different powers. The way in which political power is structured to exercise its authority in the State, coordinating all the institutions that form it, makes each form of government requires regulatory mechanisms that are characteristic of it.
There are very different nomenclatures to denominate the different forms of government, from the theorists of Antiquity to the Contemporary Age; At present, three types of classifications are usually used:
• The elective character or not of the head of state defines a classification, between republics (elective) and monarchies (non-elective).
• The degree of freedom, pluralism and political participation defines another classification, between democratic, authoritarian and totalitarian systems, depending on whether they allow the exercise of discrepancy and political opposition to a greater or lesser degree or deny more or less radically the possibility of dissidence (establishing a single-party regime, or different types of exceptional regimes, such as dictatorships or military juntas); At the same time, the electoral system through which the popular will expresses itself in participatory systems has had very different historical configurations (direct democracy or assembly, indirect or representative democracy, census or restricted suffrage, universal male suffrage or of both sexes, different determinations of the age of majority, racial segregation, inclusion or not of immigrants, and others), as well as very different ways of altering or distorting it (borgo rotido, gerrymandering, electoral fraud, pucherazo).
• The existing relationship between the head of the State, the government and the parliament defines another classification, between presidentialisms and parliamentarisms (with many degrees or mixed forms between one and the other).
These three classifications are not exclusive, but complement each other, so that a republic can be democratic (United States or South Africa) or non-democratic (China or North Korea); a republican democracy can be parliamentary (Germany or India), semi-presidential (France or Russia) or presidential (Argentina or South Korea); and a monarchy can be democratic and parliamentary (Spain, United Kingdom or Japan), undemocratic (Saudi Arabia or Vatican City) or be placed in intermediate positions (Morocco), very usually qualified in a more or less anachronistic way with terms of the historical forms of the monarchy (feudal monarchy, authoritarian monarchy, absolute monarchy).